Magnetic recording medium, method of manufacturing the same, and magnetic recording and reproduction apparatus

ABSTRACT

A magnetic recording medium includes a nonmagnetic substrate on which is provided at least a softly magnetic under-film, an orientation control film that controls an orientation of a film directly above, a perpendicular magnetic recording film having an axis of easy magnetization oriented to be mainly perpendicular to the substrate and a protective film, wherein the orientation control film is alloy containing at least Cr and C. The magnetic recording medium is manufactured by a method including carrying out, in order, at least a step of forming a softly magnetic under-film on a nonmagnetic substrate, a step of forming an orientation control film that controls an orientation of a film directly above, a step of forming a perpendicular magnetic recording film having an axis of easy magnetization oriented to be mainly perpendicular to the substrate, and a step of forming a protective film. A magnetic recording and reproduction apparatus includes the magnetic recording medium and a magnetic head that records and reproduces information on the magnetic recording medium, wherein the magnetic head is a magnetic monopole head.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is an application filed under 35 U.S.C. §111(a)claiming the benefit pursuant to 35 U.S.C. §119(e) (1) of the filingdate of Provisional Application No. 60/401,037 filed Aug. 6, 2002pursuant to 35 U.S.C. §111(b).

DETAILED DESCRIPTION OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a magnetic recording mediumenhanced in recording and reproduction characteristics and capable ofhigh-density information recording and reproduction, a method ofrmanufacturing the same, and a magnetic recording and reproductionapparatus using the magnetic recording medium.

[0004] 2. Description of Prior Art

[0005] The recording density of a hard-disk drive (HDD), which is onekind of magnetic recording and reproduction apparatus, is currentlyincreasing at an annual rate of at least 60%, and it is said that thattrend will continue. This being the case, progress is being made withthe development of magnetic recording heads suitable for high recordingdensities, and the development of magnetic recording media.

[0006] Magnetic recording media used in magnetic recording andreproduction apparatuses currently on the market are mainly in-planemagnetic recording media in which the axis of easy magnetization in themagnetic film is oriented parallel to the substrate. The axis of easymagnetization refers to the axis along which magnetization readilyoccurs. In the case of a Co-based alloy, that is the c axis of the hcpstructure of the Co.

[0007] With such an in-plane magnetic recording medium, when it comes toimplementing a high recording density, the volume of the magnetic layerper recording bit becomes too small, so the thermal fluctuation effectcan degrade the recording and reproduction characteristics. Also, whenimplementing high recording densities, media noise tends to be increasedby the effect of the demagnetizing field produced in the boundaryregions between recording bits.

[0008] In contrast, when implementing high recording density in the caseof so-called perpendicular recording media in which the axis of easymagnetization in the magnetic film is mainly perpendicular, because theeffect of the demagnetizing field in the boundary regions betweenrecording bits is small and a clear bit boundary is formed, noiseincrease can be held down. Moreover, there is only a small decrease inrecording bit density accompanying the implementation of the highrecording density, so it is not readily affected by the thermalfluctuation effect. As a result, perpendicular recording media havebecome the focus of attention in recent years, and various mediastructures are being proposed that are suited to perpendicular recordingas described below.

[0009] In recent years, the use of a magnetic monopole head, which hasan excellent ability to write to a perpendicular recording film, isbeing studied with respect to needs to further raise the recordingdensity of magnetic recording media. To use the head, it is beingproposed to use a magnetic recording medium in which the efficiency ofthe magnetic flux transfer between the magnetic monopole head and themagnetic recording medium is improved by the provision of a backinglayer constituted of what is called a softly magnetic material betweenthe perpendicular recording film constituting the recording layer andthe substrate.

[0010] However, a magnetic recording medium thus provided with just abacking layer does not have satisfactory recording and reproductioncharacteristics during recording and reproduction. What is wanted is amagnetic recording medium with excellent recording and reproductioncharacteristics.

[0011] A perpendicular magnetic recording medium generally comprises abacking layer (softly magnetic underlayer) provided on the substrate, anorientation control film that orients the axis of easy magnetization ofthe magnetic layer perpendicular to the substrate surface, aperpendicular magnetic recording film of Co alloy, and a protectivefilm, in that order. Of these, it goes without saying to use low-noisemagnetic materials for the perpendicular magnetic recording film inorder to improve the recording and reproduction characteristics of themagnetic recording medium, but with respect also to the layer structure,the following are examples of a number of proposed improvementtechniques.

[0012] Japanese Patent No. 2669529 proposes a method in which a Tiunder-film is provided between a nonmagnetic substrate and a hexagonalsystem magnetic alloy film and another element is included in the Tiunder-film to improve the lattice matching between the Ti alloyunder-film and the hexagonal system magnetic alloy film, improving the caxis orientation of the hexagonal system magnetic alloy film. However,when a Ti alloy base is used, the size of the replacement bonds withinthe alloy magnetic film increases, resulting in an increase in medianoise and making it difficult to obtain a further increase in recordingdensity.

[0013] JP-A HEI 8-180360 proposes a method in which an under-film of Coand Ru is used between a nonmagnetic substrate and a Co alloyperpendicular magnetic recording film to improve the c axis orientationof the Co alloy perpendicular magnetic recording film. However, theunder-film of Co and Ru has a large crystal grain diameter that resultsin an increase in the diameter of the magnetic particles in the Co alloymagnetic film, increasing the media noise and making it difficult toobtain a further increase in recording density.

[0014] JP-A SHO 63-211117 proposes the use of a carbon-containingunder-film between the substrate and the Co alloy perpendicular magneticrecording film. However, when a carbon-containing under-film is used,because the carbon-containing under-film has an amorphous structure, thec axis orientation of the perpendicular magnetic recording film isdegraded, degrading the resistance to thermal fluctuation and making itdifficult to obtain a further increase in recording density.

[0015] In view of the above situation, the object of the presentinvention is to provide a magnetic recording medium having improvedrecording and reproduction characteristics that enables high-densityrecording and reproduction of information, a method of manufacturing thesame, and a magnetic recording and reproduction apparatus.

SUMMARY OF THE INVENTION

[0016] To achieve the above object the present invention provides amagnetic recording medium having a nonmagnetic substrate on which isprovided at least a softly magnetic under-film, an orientation controlfilm that controls an orientation of a film directly above, aperpendicular magnetic recording film having an axis of easymagnetization oriented to be mainly perpendicular to the substrate, anda protective film, wherein the orientation control film is alloycontaining at least Cr and C.

[0017] In the magnetic recording medium, it is desirable that theorientation control film should have a C content that is not less than10 at % and not more than 80 at %.

[0018] In the magnetic recording medium, it is desirable that theorientation control film should have a C content that is not less than30 at % and not more than 70 at %.

[0019] In the magnetic recording medium, it is desirable that theorientation control film should have a Cr content that is not less than3 at % and not more than 80 at %.

[0020] In the magnetic recording medium, it is desirable that theorientation control film should have a thickness that is not less than.0.5 nm and not more than 20 nm.

[0021] In the magnetic recording medium, it is desirable that theperpendicular magnetic recording film be formed of a material containingat least Co and Pt.

[0022] The present invention further provides a method of manufacturingany one of the magnetic recording media, comprising carrying out, inorder, at least a step of forming a softly magnetic under-film on anonmagnetic substrate, a step of forming an orientation control filmthat controls an orientation of a film directly above, a step of forminga perpendicular magnetic recording film having an axis of easymagnetization oriented to be mainly perpendicular to the substrate, anda step of forming a protective film.

[0023] The invention further provides a magnetic recording andreproduction apparatus comprising any one of the magnetic recordingmedia and a magnetic head that records and reproduces information on themagnetic recording medium, wherein the magnetic head is a magneticmonopole head.

[0024] As described above, the magnetic recording medium of the presentinvention has the orientation control film containing at least Cr and C,thereby enabling the recording and reproduction characteristics to beimproved.

[0025] The above and other objects and features of the present inventionwill become apparent from the description made herein below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a cross-sectional view showing a part of an example of afirst embodiment of the magnetic recording medium of this invention.

[0027]FIG. 2 is a cross-sectional view of a part of an example of asecond embodiment of the magnetic recording medium of this invention.

[0028]FIG. 3(a) is a schematic cross section showing an example of amagnetic recording and reproduction apparatus of the present invention.

[0029]FIG. 3(b) is an enlarged view showing an example of the magnetichead of the magnetic recording and reproduction apparatus of FIG. 3(a).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030]FIG. 1 shows an example of an aspect of a first embodiment of themagnetic recording medium of the present invention. The magneticrecording medium shown in this figure comprises a softly magneticunder-film 2, an orientation control film 3, an intermediate film 4, aperpendicular magnetic recording film 5, a protective film 6 and alubricant film 7 deposited in that order on a nonmagnetic substrate 1.The configuration is described below in order from the nonmagneticsubstrate 1 side.

[0031] The nonmagnetic substrate 1 can be that of a metal material, suchas aluminum or aluminum alloy or the like, or that of a non-metallicmaterial, such as glass, ceramics, silicon, silicon carbide or carbon. Aglass substrate can be of amorphous glass or glass ceramics. Amorphousglass that can be used includes generic soda-lime glass and aluminosilicate glass. The glass ceramics used can be lithium-based glassceramics. As a ceramics substrate, there can be used a sintered bodyhaving generic aluminum oxide, aluminum nitride or silicon nitride asthe main component, or a material reinforced with fibers thereof.

[0032] To enable low head flotation suitable for high-density recording,the nonmagnetic substrate 1 should have an average surface roughness Raof not more than 2 nm (20 Å), and preferably not more than 1 nm.

[0033] To enable low head flotation suitable for high-density recording,the micro waviness (Wa) of the surface should be not more than 0.3 nm(more preferably, not more than 0.25 nm). Also the surface averageroughness Ra of edge chamfered portions and at least one side should benot more than 10 nm (more preferably, not more than 9.5 nm) from thestandpoint of head flight stability. The micro waviness (Wa) can bemeasured, as an average surface roughness within a measurement range of80 μm, using a P-12 surface roughness measurement system (manufacturedby KLA-Tencor Corporation), for example.

[0034] The softly magnetic underlayer 2 is provided to more securely fixthe magnetization direction of the perpendicular magnetic recording film5 on which information is recorded perpendicular to the nonmagneticsubstrate 1 and to increase the perpendicular component, relative to thesubstrate, of the magnetic flux generated by the magnetic head. It isdesirable for this effect to be particularly pronounced when a magneticmonopole head for perpendicular recording is used as the recording andreproduction magnetic head.

[0035] As the softly magnetic material used to form the softly magneticunder-film 2, there can be used material containing Fe. Ni and Co.Specific materials include FeCo-based alloy (FeCo, FeCoV, etc.),FeNi-based alloy (FeNi, FeNiMo, FeNiCr, FeNiSi, etc.), FeAl-based alloy(FeAl, FeAlSi, FeAlSiCr, FeAlSiTiRu, FeAlO, etc.), FeCr-based alloy(FeCr, FeCrTi, FeCrCu, etc.), FeTa-based alloy (FeTa, FeTaC, FeTaN,etc.), FeMg-based alloy (FeMgO, etc.), FeZr-based alloy (FeZrN, etc.),FeC-based alloy, FeN-based alloy, FeSi-based alloy, FeP-based alloy,FeNb-based alloy, FeHf-based alloy and FeB-based alloy. A materialhaving a fine crystal structure, such as FeAlO, FeMgO, FeTaN and FeZrN,containing 60 at % or more Fe can be used, or a material having agranular structure in which fine crystal grains are dispersed in thematrix. Materials that can be used for the softly magnetic under-film 2,in addition to the above, include Co alloy containing at least 80 at %Co and at least one selected from Zr, Nb, Ta, Cr, Mo and the like. CoZr,CoZrNb, CoZrTa, CoZrCr, CoZrMo and other such alloys are particularlysuitable.

[0036] It is desirable for the coercive force Hc of the softly magneticunder-film 2 to be not more than 100 (Oe) (more preferably, not morethan 20 (Oe)). It is undesirable for the coercive force Hc to exceed theabove range, since the softly magnetic property will then be not enoughand the reproduction waveform will be distorted from a so-called squarewave.

[0037] The product Bs·t (T·nm) of the saturation magnetic flux densityBs (T) of the softly magnetic under-film 2 and the film thickness t (nm)of the softly magnetic under-film 2 should be not less than 40 (T·nm)(more preferably, not less than 60 (T·nm)). It is undesirable for theBs·t to be less than that, as the reproduction waveform will then bedistorted and the OW characteristics degraded. The thickness of the filmlayer can be obtained by observation with a TEM (transmission electronmicroscope).

[0038] It is also desirable for the material of the surface of thesoftly magnetic under-film 2 (the surface on the orientation controlfilm 3 side) to be partially or wholly oxidized. That is, it isdesirable for the material of the surface of the softly magneticunder-film 2 (the surface on the orientation control film 3 side) andthe vicinity thereof to be partially oxidized, or for oxides of thematerial to be formed and disposed. Doing this enables magneticfluctuation of the surface of the softly magnetic under-film 2 to berestrained, reducing noise caused by such magnetic fluctuation, andthereby improving the recording and reproduction characteristics of themagnetic recording medium. Also, recording and reproductioncharacteristics can be improved by finely granulizing the crystal grainsof the orientation control film 3 formed on the softly magneticunder-film 2.

[0039] The surface of the softly magnetic under-film 2 (the surface onthe orientation control film 3 side) and the vicinity thereof canreadily be oxidized, partially or wholly, by, for example, a method inwhich the softly magnetic under-film 2 is formed and then exposed to anatmosphere containing oxygen, or a method in which oxygen is introducedduring formation of near-surface portions of the softly magneticunder-film 2. Specifically, in the case of the method in which thesurface of the softly magnetic under-film 2 is exposed to oxygen, it canbe maintained from 0.3 to 20 seconds in an oxygen atmosphere or anatmosphere in which oxygen is diluted with argon or nitrogen. It canalso be exposed to the air. Particularly when oxygen is diluted withargon or nitrogen, it is easier to adjust the degree of oxidation of thesurface of the softly magnetic under-film 2, enabling stablefabrication. Also, in the case of the method in which oxygen isintroduced into the gas used to form the film of the softly magneticunder-film 2, if sputtering, for example, is used as the film growthmethod, it is only necessary to introduce the oxygen into the processgas for just part of the film growth time. In the case of argon as theprocess gas, for example, oxygen can be mixed at a volumetric ratio of0.05% to 50% (preferably, 0.1 to 20%).

[0040] The orientation control film 3 controls the orientation and graindiameter of the above intermediate film 4 and/or perpendicular magneticrecording film 5. In the magnetic recording medium of this invention,the orientation control film 3 is composed of material containing atleast Cr and C.

[0041] It is desirable for the orientation control film 3 to furthercontain one, two or more elements, in addition to Cr and C, notrestricted but preferably selected from Ti, Zr, Hf, V, Nb, Ta, Mo and W.It is undesirable for the orientation control film not to contain eitherCr or C because the recording and reproduction characteristics becomeinsufficient.

[0042] It is also desirable for the orientation control film 3 to have aC content of not less than 10 at % and not more than 80 at %(preferably, not less than 30 at % and not more than 70 at %). When theC content is within the above range, the recording and reproductioncharacteristics are particularly excellent.

[0043] It is further desirable for the orientation control film 3 tohave a Cr content of not less than 3 at % and not more than 80 at %(preferably, not less than 5 at % and not more than 50 at %). When theCr content is within the above range, the recording and reproductioncharacteristics are particularly excellent.

[0044] Further, the orientation control film 3 should have a thicknessof not less than 0.5 nm and not more than 20 nm (more preferably, 1 to12 nm). When the thickness of the orientation control film 3 is withinthis range, the perpendicular orientation of the perpendicular magneticrecording film 5 becomes particularly high, and the distance between themagnetic head and the softly magnetic under-film 2 during recording canbe made small, making it possible to enhance the recording andreproduction characteristics without reducing the resolution of thereproduction signal. If the thickness is less than this range, theperpendicular orientation in the perpendicular magnetic recording film 5is reduced, degrading the recording and reproduction characteristics andthe resistance to thermal fluctuation. If this thickness range isexceeded, the perpendicular orientation of the perpendicular magneticrecording film 5 is reduced, degrading the recording and reproductioncharacteristics and the resistance to thermal fluctuation. Moreover, thedistance between the magnetic head and the softly magnetic under-film 2during recording is increased, which is not desirable since thereproduction signal resolution and reproduction output is lowered.

[0045] The orientation control film 3 is preferably formed as anamorphous or fine crystal structure, which enables the orientation ofthe intermediate film 4 and/or the perpendicular magnetic recording film5 provided directly above it to be improved and the particle diameter tobecome fine. The crystal structure can be confirmed by using the X-raydiffraction method or a transmission electron microscope (TEM).

[0046] The shape of the surface of the orientation control film 3affects the surface shapes of the perpendicular magnetic recording film5 and protective film 6, so to reduce the unevenness of the magneticrecording medium and reduce the head flotation height during recordingand reproduction, it is desirable for the orientation control film 3 tohave an average surface roughness Ra of not more than 2 nm. Using anaverage surface roughness Ra of not more than 2 nm reduces the surfaceunevenness of the magnetic recording medium and enables the flotationheight of the magnetic head during recording and reproduction to besufficiently reduced, increasing the recording density.

[0047] With respect to the gas used to grow the orientation control film3, it is desirable to use a process gas containing oxygen or nitrogen torefine the perpendicular magnetic recording film formed thereon If thefilm is formed using the sputtering method, for example, as thefilm-growing method, it is desirable to use oxygen mixed with argon at avolumetric ratio of 0.05 to 50% (more preferably, 0.1 to 20%), ornitrogen mixed with argon at a volumetric ratio of 0.01 to 20% (morepreferably, 0.02 to 10%).

[0048] As shown in the illustrated example, an intermediate film 4 canbe provided between the orientation control film 3 and the perpendicularmagnetic recording film. For this intermediate film 4, it is desirableto use a material having an hcp structure, with CoCr alloy, CoCrY1 alloyor CoY1 alloy (Y1: one, two or more selected from Pt, Ta, Zr, Ru, Nb,Cu, Re, Ni, Mn, Ge, Si, O, N and B) being particularly suitable. Theintermediate film 4 should preferably contain 30 to 70 at % Co. Theintermediate film 4 should preferably be not more than 30 nm thick (morepreferably, not more than 20 nm) to prevent the recording andreproduction characteristics being deteriorated by coarsening of themagnetic particles in the perpendicular magnetic recording film 5, andto prevent the recording resolution being reduced by an increase in thedistance between the magnetic head and the softly magnetic under-film 2.Thus, providing the intermediate film 4 enables the perpendicularorientation of the perpendicular magnetic recording film 5 to beincreased, raising the coercive force of the perpendicular magneticrecording film 5 and further improving the recording and reproductioncharacteristics and the resistance to thermal fluctuation.

[0049] The axis of easy magnetization of the perpendicular magneticrecording film 5 is oriented mainly perpendicular to the substrate, andthe film preferably is formed of a material containing at least Cr andPt. It is desirable to form it of a material containing at least Cr andPt, the Cr content being not less than 14 at % and not more than 24 at %(more preferably, not less than 16 at % and not more than 22 at %), andthe Pt content being not less than 14 at % and not more than 24 at %(more preferably, not less than 15 at % and not more than 20 at %). Bymainly perpendicular is meant a perpendicular magnetic recording film inwhich perpendicular coercive force Hc (P) and in-plane coercive force Hc(L) are Hc (P)>Hc (L). It is also desirable to use a material containingnot less than 0.1 and not more than 5 at % B. This enables the exchangecouplings between magnetic particles to be reduced, making it possibleto improve the recording and reproduction characteristics. It isundesirable for the material composition to have a Cr content that isless than 14 at %, since the exchange couplings between the magneticparticles will then be increased, increasing the diameter of themagnetic clusters and thereby increasing the noise. It is also notdesirable for the Cr content to be more than 24 at %, since that willreduce the ratio Mr/Ms between remanent magnetization (Mr) andsaturation magnetization (Ms). If the Pt content is less than 14 at %,the improvement effect on the recording and reproduction characteristicswill not be sufficient, lowering the Mr/Ms ratio between the remanentmagnetization (Mr) and the saturation magnetization (Ms) and theresistance to thermal fluctuation. A Pt content that is more than 24 at% is not desirable, since noise will increase.

[0050] When the perpendicular magnetic recording film 5 is formed ofCoCrPt-based alloy, any element other than B can be added as desired.There is no particular limitation, but V, Ta, Mo, Nb, Hf, Cu, Ru, Nd,Zr, W, Nd, Si and O are among those that can be mentioned.

[0051] The perpendicular magnetic recording film 5 can be, a one-layerstructure comprised of CoPt-based, material, or a structure comprised oftwo or more layers of materials having different compositions. In thecase of a structure of two or more layers, a multilayer structure can beused comprised of layers of Co-based alloy (CoCr, CoB, Co—SiO₂, etc.)and Pd-based alloy (PdB, Pd—SiO₂, etc.), or comprised of amorphousmaterial, such as CoTb and CoNd, and CoCrPt-based material. Or,CoPt-based material can be provided as a first perpendicular magneticrecording film, and CoPt-based material having a different compositionas a second perpendicular magnetic recording film. Also, CoPt-basedmaterial can be provided as a first perpendicular magnetic recordingfilm, and CoNd as a second perpendicular magnetic recording film.

[0052] It is desirable for the thickness of the perpendicular magneticrecording film 5 to be 7 to 60 nm (more preferably, 10 to 40 nm). Aperpendicular magnetic recording film 5 thickness of 7 nm or more isdesirable, since sufficient magnetic flux can be obtained, there is nodecrease in output during reproduction, and there is no eddy leakage inthe noise component of the output waveform, resulting in magneticrecording and reproduction apparatus operation suitable for higherrecording density. Also, a perpendicular magnetic recording film 5thickness that is not more than 60 nm is desirable, since it enablescoarsening of the magnetic particles in the perpendicular magneticrecording film 5 to be suppressed, so there is no risk of degradation ofrecording and reproduction characteristics caused by increased noise.

[0053] It is desirable for the perpendicular magnetic recording film 5to have a coercive force of not less than 3000 (Oe). A coercive forcethat is less than 3000 (Oe) is undesirable since it prevents theobtaining of the necessary high recording density resolution, and alsodegrades the resistance to thermal fluctuation.

[0054] In addition, it is also desirable for the ratio Mr/Ms between theremanent magnetization (Mr) and the saturation magnetization (Ms) of theperpendicular magnetic recording film 5 to be not less than 0.9. AnMr/Ms ratio of less than 0.9 is undesirable because it degrades thethermal fluctuation resistance of the magnetic recording medium.

[0055] It is also desirable for the inverse magnetic domain nucleationfield (-Hn) of the perpendicular magnetic recording film 5 to be notless than 0 and not more than 2500 (Oe). It is undesirable for themagnetic recording medium to have an inverse magnetic domain nucleationfield (-Hn) that is less than 0, since thermal fluctuation resistance isdegraded. The upper limit of the inverse magnetic domain nucleationfield (-Hn) is set at 2500 (Oe). An attempt to obtain a higher inversemagnetic domain nucleation field (-Hn) can result in the magneticparticles having insufficient magnetic separation, increasing the activemagnetic moment (vIsb) and producing an increase in noise duringrecording and reproduction.

[0056] It is desirable for the crystal grains of the perpendicularmagnetic recording film 5 to have an average grain diameter of 5 to 15nm. The average grain diameter can be obtained through observing thecrystal grains of the perpendicular magnetic recording film 5 with a TEM(transmission electron microscope) and processing the observed images.

[0057] It is desirable for the ΔHc/Hc of the perpendicular magneticrecording film 5 to be not more than 0.3. A ΔHc/Hc of not more than 0.3is desirable since it reduces variation in the diameter of the magneticparticles, producing a more uniform coercive force in the perpendiculardirection of the perpendicular magnetic recording film, and thereforedeterioration of the recording and reproduction characteristics andthermal fluctuation resistance can be held in check.

[0058] The protective film 6 protects the perpendicular magneticrecording film 5 from corrosion and also protects the medium surfacefrom damage when the magnetic head contacts the medium. The protectivefilm 6 can be formed of a conventional, known material, such as onecontaining C, SiO₂ and ZrO₂. From the standpoint of high recordingdensity, it is desirable for the protective film 6 to have a thicknessset at 1 to 10 nm, since this makes it possible to reduce the distancebetween the head and the perpendicular magnetic recording film 5.

[0059] For the lubricant film 7, it is desirable to use a conventional,known material, such as perfluoropolyether, alcohol fluorine, carboxylicacid fluorine, etc.

[0060] The magnetic recording medium constituted of the layers eachhaving the configuration as mentioned above, which is the firstinvention of the present invention, has an orientation control filmformed of alloy containing at least Cr and C, improving the recordingand reproduction characteristics (lower noise, for example) when used athigher recording densities, thus forming a magnetic recording mediumthat enables high-density information recording and reproduction.

[0061]FIG. 2 shows an example of an aspect of a second embodiment of themagnetic recording medium of the present invention, in which a permanentmagnetic film 8 with mainly in-plane oriented magnetic anisotropy isprovided between the nonmagnetic substrate 1 and the softly magneticunder-film 2 of the first embodiment.

[0062] The permanent magnetic film 8 can be formed of CoSm alloy orCoCrPtY2 alloy (Y2: one, two or more selected from Pt, Ta, Zr, Nb, Cu,Re, Ni, Mn, Ge, Si, O, N and B) being suitable. It is desirable for thecoercive force Hc of the permanent magnetic film 8 to be not less than500 (Oe) (more preferably, not less than 1000 (Oe)). It is alsodesirable for the permanent magnetic film 8 to have a thickness that isnot more than 150 nm (more preferably, not more than 70 nm). It isundesirable for the thickness to exceed 150 nm, since it would increasethe average surface roughness Ra of the orientation control film 3. Itis also desirable for the permanent magnetic film 8 to be composed to beexchange-coupled to the softly magnetic under-film 2, with magnetizationoriented in the radial direction of the substrate.

[0063] Providing the permanent magnetic film 8 enables the formation ofgiant magnetic domains in the softly magnetic under-film 2 to be moreeffectively controlled, preventing noise spikes from the magnetic wallsand adequately lowering the error rate during recording andreproduction.

[0064] A B2 structure material or Cr alloy material can be used betweenthe nonmagnetic substrate 1 and the permanent magnetic film 8 to controlthe orientation of the permanent magnetic film 8.

[0065] Next, an example of a method of manufacturing the magneticrecording medium according to the first (and second) embodiments will bedescribed. First, the softly magnetic under-film 2 is formed on thenonmagnetic substrate 1 by a method, such as sputtering. Then, ifrequired, the surface of the softly magnetic under-film 2 and thevicinity thereof are partially or wholly oxidized. Next, a method, suchas sputtering, is used to form the orientation control film 3,intermediate film 4 and perpendicular magnetic recording film 5. Then,the protective film 6 is formed by a method, such as the CVD method,ion-beam method or sputtering method. Then, the lubricant film 7 isformed by the dipping method, spin-coating method or the like. Whenmanufacturing the magnetic recording medium of the second embodiment,the step of forming the permanent magnetic film 8 between thenonmagnetic substrate 1 and the softly magnetic under-film 2 can beincluded. Below, each process is explained.

[0066] If required, the nonmagnetic substrate I is washed and thenonmagnetic substrate 1 is placed in the chamber of the film formationapparatus. Also, if required, a heater, for example, is used to heat thenonmagnetic substrate 1 to a temperature of 100 to 400° C. Then, thesoftly magnetic under-film 2, orientation control film 3, intermediatefilm 4 and perpendicular magnetic recording film 5 are formed on thenonmagnetic substrate 1 by DC or RF magnetron sputtering using a sputtertarget of a material having the same composition as the material of eachlayer. The sputtering conditions used to form the films are set asfollows, for example. The chamber used for the formation is evacuated toa vacuum of 10⁻⁵ to 10⁻⁷ Pa. The nonmagnetic substrate 1 is placed inthe chamber and Ar gas, for example, as the sputter gas, is introducedand a discharge used to perform sputter film formation. The powersupplied at this time is 0.2 to 5 kW, and the discharge time andsupplied power are regulated to obtain the desired film thickness.Specifically, a film thickness of 50 to 400 nm is desirable.

[0067] In forming the softly magnetic under-film 2, it is desirable touse sputter targets (fused alloy targets or sintered alloy targets) madeof the types of softly magnetic material described above, to facilitateformation of the softly magnetic under-film.

[0068] After forming the softly magnetic under-film 2, it is desirableto carry out the aforementioned process of partially or wholly oxidizingthe surface thereof (on the orientation control film 3 side) by, forexample, using a method in which, after the softly magnetic under-film 2is formed, it is exposed to an oxygen-containing atmosphere, or a methodin which oxygen is introduced into the process during growth ofnear-surface portions of the softly magnetic under-film 2.

[0069] After forming the softly magnetic under-film 2, the orientationcontrol film 3 is formed to a film thickness of 1 to 20 nm (morepreferably, 1 to 10 nm) by regulating the discharge time and suppliedpower.

[0070] In forming the orientation control film-3, it is desirable to usea sputter target made of the type of orientation control film materialdescribed above, to facilitate formation of the orientation controlfilm. The sputter target material used to form the orientation controlfilm 3 is an alloy containing at least Cr and C.

[0071] As already described, oxygen or nitrogen can be introduced intothe gas used to grow the orientation control film 3 with the aim ofrefining the perpendicular magnetic recording film.

[0072] The perpendicular magnetic recording film 5 is formed afterforming the orientation control film 3. In forming the perpendicularmagnetic recording film, it is desirable to use a sputter target made ofthe type of perpendicular magnetic recording film material describedabove, to facilitate formation of the perpendicular magnetic recordingfilm. Specifically, it is desirable for the sputter target material tohave a composition containing as the main component CoCrPt wherein a Crcontent is not less than 14 at % and not more than 24 at % and a Ptcontent is not less than 14 at % and not more than 24 at %.

[0073] As already described, an intermediate film 4 can be providedbetween the orientation control film 3 and the perpendicular magneticrecording film 5 to increase the perpendicular orientation of theperpendicular magnetic recording film 5 and increase the coercive forceof the perpendicular magnetic recording film 5, to further improverecording and reproduction characteristics and thermal fluctuationresistance.

[0074] After forming the perpendicular magnetic recording film 5, thesputtering method or plasma CVD method, or a combination thereof, forexample, is used to form the protective film 6, such as a protectivefilm having carbon as the main component.

[0075] Also, if required, a lubricant film 7 of perfluoropolyether orother such fluorine-based lubricating agent can be applied onto theprotective film 6 by a method, such as dipping or spin coating.

[0076] The magnetic recording medium manufactured by the method ofmanufacturing the magnetic recording medium that is the second inventionof the present invention constituted of these processes, and which canbe implemented using the sputtering method or the like, is a magneticrecording medium in which the orientation control film 3 is formed ofalloy containing at least Cr and C, improving the recording andreproduction characteristics (lower noise, for example) when used athigher recording densities, thus forming a magnetic recording mediumthat enables high-density information recording and reproduction.

[0077]FIG. 3 shows an example of a magnetic recording and reproductionapparatus, which is an example of an aspect of the third invention ofthe present invention, using a magnetic recording medium that is thefirst invention and is manufactured in accordance with the secondinvention. The magnetic recording and reproduction apparatus shown hereincludes a magnetic recording medium 9, a medium drive section 10 thatrotates the magnetic recording medium 9, a magnetic head 11 that recordsinformation on the magnetic recording medium 9 and reproduces therecording, a head drive section 12 and a recording and reproductionsignal processing system 13. The recording and reproduction signalprocessing system 13 is able to process input data and send recordingsignals to the magnetic head 11, and process reproduction signals fromthe magnetic head 11 and output the data. The magnetic head 11 can, forexample, be a magnetic monopole head for perpendicular recordingapplications. A suitable magnetic monopole head is one, as shown in FIG.3(a), having a configuration provided with a main pole lla, an auxiliarypole 11 b, a connecting section 11 c that connects these, and a coil 11d provided on the connecting section 11 c.

[0078] This magnetic recording and reproduction apparatus uses themagnetic recording medium 9 having the aforementioned configuration,enabling the recording and reproduction characteristics to be improvedand preventing troubles, such as date disappearance, owing to thermalfluctuation from occurring, helping to achieve high recording density.

[0079] Examples are shown below to clarify the action and effect of thepresent invention, but the invention is not limited to these Examples.

EXAMPLE 1

[0080] A washed glass substrate (manufactured by Ohara Inc., Japan, withan outside diameter of 2.5 inches) was placed in the film formationchamber of the DC magnetron sputter apparatus (C-3010 manufactured byAnelva Corp., Japan). After the film formation chamber was evacuateduntil a vacuum of 1×10⁻⁵ Pa was achieved, using an 89Co-4Zr-7Nb (Cocontent 89 at %, Zr content 4 at %, Nb content 7 at %) target, a 160-nmsoftly magnetic under-film 2 was formed on the glass substrate by thesputtering method. Using a vibrating sample magnetometer (VSM), theproduct Bs·t (T·nm) of the saturation magnetic flux density Bs (T) ofthe film and the film thickness t (nm) was confirmed to be 200 (T·nm).Next, the substrate was heated to 240° C. and a 30Cr-50C-20W target wasused to form an 5-nm orientation control film on the softly magneticunder-film. A 65Co-30Cr-5B (Co content 65 at %, Cr content 30 at %, Bcontent 5 at %) target was used to form a 10-nm intermediate film, and a64Co-17Cr-17Pt-2B (Co content 64 at %, Cr content 17 at %, Pt content 17at %, B content 2 at %) target was then used to form a 20-nmperpendicular magnetic recording film. For the above sputtering process,argon was used as the film growth process gas, and the film was formedat a pressure of 0.6 Pa. Next, the CVD method was used to form a 5-nmprotective film 6. Next, the dipping method was used to form a lubricantfilm of perfluoropolyether, to thereby obtain a magnetic recordingmedium. The contents thereof are shown in Table 1.

COMPARATIVE EXAMPLES 1 TO 3

[0081] Except that 60Ru-40Co, Ti and C targets were used, Example 1 wasused as a basis for fabricating magnetic recording media. The contentsare shown in Table 1.

[0082] Recording and reproduction characteristics of the magneticrecording media of Example 1 and Comparative Examples 1 to 3 wereevaluated. For the evaluation of the recording and reproductioncharacteristics, measurements were made with the RWA1632 Read/WriteAnalyzer and the S1701 MP Spin-Stand manufactured by Guzik Corp. of theU.S. For the evaluation of the recording and reproductioncharacteristics, a head was used having a single-pole for writes and areproduction section with a GMR element, and measurements were takenusing a linear recording density of 600 kFCI as the recording frequencycondition. Test results are shown in Table 1. TABLE 1 PerpendicularMagnetic Softly Magnetic Orientation Control Film Intermediate FilmRecording Film Under-film Thick- Thick- Thick- Compo- Bs x t Compositionness Composition ness Composition ness sition (T nm) (at %) (nm) (at %)(nm) (at %) (nm) Example CoZrNb 200 30Cr—50C—20W 5 65Co—30Cr—5B 1064Co—17Cr—17Pt—2B 20 1 Comp. CoZrNb 200 60Ru—40Co 15 65Co—30Cr—5B 1064Co—17Cr—17Pt—2B 20 Example 1 Comp. CoZrNb 200 Ti 20 65Co—30Cr—5B 1064Co—17Cr—17Pt—2B 20 Example 2 Comp. CoZrNb 200 C 5 65Co—30Cr—5B 1064Co—17Cr—17Pt—2B 20 Example 3 Recording/ Reproduction CharacteristicsError rate Hc —Hn (10^(x)) (Oe) Mr/Ms (Oe) Example −5.6 4255 1.00 500 1Comp. −4.1 4250 0.77 100 Example 1 Comp. −2.1 3590 1.00 400 Example 2Comp. −3.2 3760 0.88 100 Example 3

[0083] As is clear from Table 1, the magnetic recording medium ofExample 1 in which the orientation control film was formed of30Cr-50C-20W alloy, exhibited superior recording and reproductioncharacteristics to Comparative Examples 1 to 3.

EXAMPLES 2 to 13

[0084] Example 1 was used as a basis for fabricating magnetic recordingmedia of Examples 2 to 13, except for the composition of the orientationcontrol film as shown in Table 2. For the sake of comparison, theintermediate film and perpendicular magnetic recording film were giventhe same composition and thickness.

[0085] Recording and reproduction characteristics of the magneticrecording media of Examples 2 to 13 were evaluated. Test results areshown in Table 2. TABLE 2 Softly Magnetic Orientation IntermediateUnder-film Control Film Film Bs x t Composition Thickness CompositionThickness Composition (T nm) (at %) (nm) (at %) (nm) Example 1 CoZrNb200 35Cr—45C—20W 5 65Co—30Cr—5B 10 Example 2 CoZrNb 200 25Cr—75C 565Co—30Cr—5B 10 Example 3 CoZrNb 200 35Cr—65C 5 65Co—30Cr—5B 10 Example4 CoZrNb 200 65Cr—35C 5 65Co—30Cr—5B 10 Example 5 CoZrNb 20075Cr—15C—10W 5 65Co—30Cr—5B 10 Example 6 CoZrNb 200 35Cr—45C—20Ti 565Co—30Cr—5B 10 Example 7 CoZrNb 200 35Cr—45C—20Zr 5 65Co—30Cr—5B 10Example 8 CoZrNb 200 35Cr—45C—20Hf 5 65Co—30Cr—5B 10 Example 9 CoZrNh200 35Cr—45C—20V 5 65Co—30Cr—5B 10 Example 10 CoZrNh 200 35Cr—45C—20Nh 565Co—30Cr—5B 10 Example 11 CoZrNb 200 35Cr—4SC—20Ta 5 65Co—30Cr—SB 10Example 12 CoZrNb 200 35Cr—45C—20Mo 5 65Co—30Cr—5B 10 Example 13 CoZrNh200 5Cr—65C—30W 5 65Co—30Cr—SB 10 Perpendicular MagneticRecording/Reproduction Recording Film Characteristics CompositionThickness Error rate (at %) nm (10^(x)) Example 1 64Co—17Cr—17P1—2B 20−5.6 Example 2 64Co—17Cr—17Pt—2B 20 −5.1 Example 3 64Co—17Cr—17Pt—2B 20−5.3 Example 4 64Co—17Cr—17Pt—2B 20 −5.4 Example 5 64Co—17Cr—17Pt—2B 20−5.2 Example 6 64Co—17Cr—17Pt—2B 20 −5.5 Example 7 64Co—17Cr—17Pt—2B 20−5.7 Example 8 64Co—17Cr—17Pt—2B 20 −5.3 Example 9 64Co—17Cr—17Pt—2B 20−5.6 Example 10 64Co—17Cr—17Pt—2B 20 −5.6 Example 11 64Co—17Cr—17Pt—2B20 −5.6 Example 12 64Co—17Cr—17Pt—2B 20 −5.8 Example 1364Co—17Cr—17Pt—2B 20 −5.1

[0086] As is clear from Table 2, the magnetic recording media ofExamples 2 to 13 in which the orientation control film had a compositionof Cr—C—X, exhibited superior recording and reproductioncharacteristics.

EXAMPLES 14 to 18

[0087] Example 1 was used as a basis for fabricating magnetic recordingmedia of Examples 14 to 18, except for the thickness of the orientationcontrol film as shown in Table 3. For the sake of comparison, theorientation control films were given the same composition. Also, thesoftly magnetic under-film, intermediate film and perpendicular magneticrecording film were given the same composition and thickness.

[0088] Recording and reproduction characteristics of the magneticrecording media of Examples 14 to 18 were evaluated. Test results areshown in Table 3. TABLE 3 Softly Magnetic Orientation IntermediateUnder-film Control Film Film Bs x t Composition Thickness CompositionThickness Composition (T nm) (at %) (nm) (at %) (nm) Example 1 CoZrNh200 35Cr—45C—20W 5 65Co—30Cr—5B 10 Example 14 CoZrNb 200 35Cr—45C—20W0.6 65Co—30Cr—5B 10 Example 15 CoZrNb 200 35Cr—45C—20W 1.5 65Co—30Cr—5B10 Example 16 CoZrNb 200 35Cr—45C—20W 11 65Co—30Cr—5B 10 Example 17CoZrNb 200 35Cr—45C—20W 18 65Co—30Cr—5B 10 Example 10 CoZrNb 20035Cr—45C—20W 30 65Co—30Cr—SB 10 Perpendicular MagneticRecording/Reproduction Recording Film Characteristics CompositionThickness (Error rate) (at %) (nm) (10^(x)) Example 1 64Co—17Cr—17Pt—2B20 −5.6 Example 14 64Co—17Cr—17Pt—2B 20 −5.2 Example 1564Co—17Cr—17Pt—2B 20 −5.4 Example 16 64Co—17Cr—17Pt—2B 20 −5.3 Example17 64Co—17Cr—17Pt—2B 20 −5.2 Example 10 64Co—17Cr—17Pt—2B 20 −4.9

[0089] As is clear from Table 3, the magnetic recording media ofExamples 14 to 17 in which the thickness of the orientation control filmwas not less than 0.5 nm and not more than 20 nm (particularly not lessthan 1 nm and not more than 12 nm in Examples 15 and 16) showedparticularly good recording and reproduction characteristics.

[0090] As described in the foregoing, the magnetic recording medium ofthe present invention comprises, on a nonmagnetic substrate, at least asoftly magnetic under-film, an orientation control film for controllingorientation of the film above, a perpendicular magnetic recording filmhaving an axis of easy magnetization oriented mainly perpendicular tothe substrate and a protective film, in which the orientation controlfilm is composed of alloy containing at least Cr and C, enabling therecording and reproduction characteristics to be improved.

What is claimed is:
 1. A magnetic recording medium having a nonmagneticsubstrate on which is provided at least a softly magnetic under-film, anorientation control film that controls an orientation of a film directlyabove, a perpendicular magnetic recording film having an axis of easymagnetization oriented to be mainly perpendicular to the substrate, anda protective film, wherein the orientation control film is alloycontaining at least Cr and C.
 2. The magnetic recording medium accordingto claim 1, wherein the orientation control film has a C content that isnot less than 10 at % and not more than 80 at %.
 3. The magneticrecording medium according to claim 1, wherein the orientation controlfilm has a C content that is not less than 30 at % and not more than 70at %.
 4. The magnetic recording medium according to claim 1, wherein theorientation control film has a Cr content that is not less than 3 at %and not more than 80 at %.
 5. The magnetic recording medium according toclaim 1, wherein the orientation control film has a thickness that isnot less than 0.5 nm and not more than 20 nm.
 6. The magnetic recordingmedium according to claim 2, wherein the orientation control film has athickness that is not less than 0.5 nm and not more than 20 nm.
 7. Themagnetic recording medium according to claim 1, wherein theperpendicular magnetic recording film is formed of a material containingat least Co and Pt.
 8. The magnetic recording medium according to claim2, wherein the perpendicular magnetic recording film is formed of amaterial containing at least Co and Pt.
 9. A method of manufacturing themagnetic recording medium according to claim 1, comprising carrying out,in order, at least a step of forming a softly magnetic under-film on anonmagnetic substrate, a step of forming an orientation control filmthat controls an orientation of a film directly above, a step of forminga perpendicular magnetic recording film having an axis of easymagnetization oriented to be mainly perpendicular to the substrate, anda step of forming a protective film.
 10. A method of manufacturing themagnetic recording medium according to claim 2, comprising carrying out,in order, at least a step of forming a softly magnetic under-film on anonmagnetic substrate, a step of forming an orientation control filmthat controls an orientation of a film directly above, a step of forminga perpendicular magnetic recording film having an axis of easymagnetization oriented to be mainly perpendicular to the substrate, anda step of forming a protective film.
 11. A magnetic recording andreproduction apparatus comprising the magnetic recording mediumaccording to claim 1 and a magnetic head that records and reproducesinformation on the magnetic recording medium, wherein the magnetic headis a magnetic monopole head.
 12. A magnetic recording and reproductionapparatus comprising the magnetic recording medium according to claim 2and a magnetic head that records and reproduces information on themagnetic recording medium, wherein the magnetic head is a magneticmonopole head.